Joint replacement surgery is a common orthopedic procedure for joints such as the shoulder, hip, knee, ankle and wrist. Prior to implanting prosthetic components in a joint of a patient, a surgeon generally has to resect at least a portion of the patient's native bone in order to create a recess or void for receiving at least a portion of the prosthetic components being implanted. During the process of resecting bone, a surgeon generally only resects the amount of bone that is needed in order to properly implant the prosthetic components in the joint. Once native bone is resected from a joint, it is gone forever. Thus, the surgeon typically attempts to maintain as much native structural integrity of the joint as he or she can during the resection process.
When previously implanted prosthetic components fail for any one of a variety of reasons, a revision procedure is often necessary. An issue generally encountered by surgeons replacing joints during a revision procedure is the additional loss of native bone near the joint being replaced. This bone loss is typically due to movement of the component or components after implantation or even degeneration or further degeneration of the bone, which can form bone voids that have unpredictable and non-uniform shapes.
When bone voids are observed in either the proximal tibia or distal femur, or both, it is standard surgical practice to fill those voids as part of the revision surgical procedure. The preferred practice is to fill those voids with weight bearing void fillers, typically made of an implant-grade metal such as titanium. However, because the bone voids are typically irregular in shape, some preparation of the bone void area is typically required prior to implantation of the void filler. This preparation (typically by reaming, broaching or milling) ensures there is sufficient room in the bone void for the void filler. An accurate fit between the shaped bone void and the void filler is also important for establishing joint line, and allowing for weight bearing and bone remodeling during the recovery process.
Different methods are commonly used to attempt to prepare the bone void area to create an accurate fit between the shaped bone void and void filler. One method is to ream along the intramedullary (“IM”) axis, followed by broaching. Another method is to ream along the IM axis, followed by freehand burring or rongeur bone removal, which may also be followed by broaching. Problems with these methods include that reaming is performed on the IM axis only, so that void areas at a distance from the IM axis, which commonly occur, can only be resected using manual methods. Moreover, broaching generally has at least two problems. First, a manual operation can be time consuming, particularly in cases of sclerotic bone, which exposes the patient to an increased risk of infection and longer recovery. Second, in the case of large bone voids, broaching generally needs to be performed in a multi-step process because attempting to remove high volumes of bone in a single broaching step generally requires high impact forces to the bone. Also, freehand bone removal, either powered or unpowered, such as with a burr or rongeur, often does not produce accurate void shapes to receive predefined prosthetic components. A typical result is that areas remain where the outer walls of the void filler do not contact the void, which may lead to undesirable stress distribution and possible loss of bone regrowth. Also typical is the time consuming requirement of iterative bone removal, with multiple checks against the void fillers, to obtain a correct fit.
Occasionally the bone loss or bone deformity is so significant that the surgeon must resect a portion of bone along its length and supplement the bone loss with a bone augment. Since the surgeon typically attempts to preserve as much native bone as possible, the result of the resection is typically a bone that has multilevel plateaus, where the bone augment is commonly placed between the joint prosthesis and one plateau in order to augment the missing bone, and the prosthesis itself is placed against the other plateau. However, this resection generally does not eliminate the need for a void filler. Generally, the bone void extends through the multilevel plateaus, which creates an area where the void filler would be exposed and would interfere with the placement of the bone augment when implanted. Unfortunately, this situation is often unpredictable as the surgeon is often unaware of the need to augment until the previous prosthesis has been removed.
Thus, there is a need for a bone void filler that is adaptable to be used in both a joint revision procedure requiring a bone augment so as to not interfere with the placement of the augment and a joint revision procedure where a bone augment is not needed.